I’m trying to add an @supports rule to my stylesheet, however MT doesn’t appear to support this and won’t save it. Is there a way to force MT to save it anyway? Or an alternative way to add this rule? I’ve noticed this before with certain other (non at-rule CSS) styles it doesn’t recognize and consequently save.
The code editor to the left of the Font property group only support single selectors. You can’t add other CSS rules like @support, @media, @font-face etc. However, you can add that code via the full code view:
Settings > View > Full code editor
And in a future update, you will be able to add CSS/Sass snippets to folders in the main UI view for adding raw code more freely.